gdbstub initial code

[Roland McGrath]

> What is the reasoning for selecting /proc/ugdb instead of something like
> /proc/<pid>/ugdb?

The protocol, and gdb, support dealing with many processes over one control
channel.  For normal the debugger model to work where it can attach to a
process on demand, with your model it would have to open another fd for
every process (or perhaps thread), maintain perhaps thousands of fds, do a
select dance, never be able to pipeline notifications from multiple
processes into a single receiving call in the debugger, etc.  Moreover,
that's just not what the protocol is and we already have a protocol with a
client that we can just support as is.


Thanks,
Roland